my unit is an SEL AWD and did not come with a towing hitch on the back end. I have the tranny cooler installed from factory, Is there anything I need to upgrade before I put in a reciever hitch on the unit?

I have the same issue, I was told by a body shop this week that the rear bumper is a two-peice bumper with the bottom part being different for the tow package. You will need to buy the bottom part with a cuttout for the hitch in the center of the bumper, and also, there is a re-bar that has to be installed under the vehicle to which the hitch is attached.